The present invention relates to a hybrid synchronous motor with toroidal winding. In particular, the present invention pertains to a hybrid synchronous motor having a structure that can provides higher torque per machine weight as compared to conventional motors with similar construction.
Hybrid electric machines are stepper motors with in-built permanent magnets that increase magnetic field density in the air gap. Special constructions of such motors are already known. One such construction exhibits cogged iron rings in both the stator and the rotor wherein the stator coils are wound like in many other stepper motors and are typically three-phase. Further, strong permanent magnets in the form of discs are inserted in between iron sheets (lamellae) of the stator and magnetized in the axial direction in such a way that magnetic flux of the permanent magnets passes across the iron sheets while the magnetic flux of the coils goes along the sheets in the longitudinal direction. With such a construction, a relatively high magnetic flux density may be obtained in the air gap, and hence, high torque per machine weight.
According to another construction, the motors are provided with a double air gap between the rotor and stator, i.e. an inner air gap and an outer air gap. They have a rotor ring with cogs on both the inner and the outer circumference and contain two stator rings, an inner and an outer one. Each of these two stator rings is in its construction similar to the construction described above so that the number of coils is doubled, and concurrently the number of permanent magnets.
The motors according to the above described constructional solutions have a relatively good torque per weight. The second construction described above gives double torque because the active surface at the air gap is also doubled. Yet this embodiment harbors the shortcoming in that the motor needs a double number of stator coils and a double number of stator permanent magnets with the result that ohmic losses in the coils are also doubled. Consequently, there was a need in the art for additional hybrid synchronous motors having a high torque per weight, yet avoiding the disadvantages of the prior art.
An object of the present invention resides therefore in providing a hybrid synchronous motor with double (inner and outer) air gaps, which is able to generate a high density magnetic field in the air gap by combining the transverse magnetic flux of permanent magnets and the longitudinal magnetic flux of stator coils.
In order to realize the above object, according to the present invention, there is provided a hybrid synchronous motor with toroidal winding comprising a rotor and a stator, the stator comprising of at least one assembly of coxially displaced ferromagnetic rings which are cogged both on inner and outer circumferences thereof, the assembly being provided with a polyphase toroidal coil made of coil segments so that the coil wire is lying between cogs.
The hybrid synchronous motor according to the present invention exhibits a high magnetic flux density in the air gap as the result of transverse magnetic flux of the permanent magnets combined with longitudinal magnetic flux of the coils and high active surface at the air gap due to double (inner and outer) air gaps, yet contains only a single set of stator coils. Since merely a small number of assembling parts and conventional techniques of fabrication may be applied, the motor is cheap in construction. Further, the motor exhibits an excellent energy efficiency due to only small ohmic losses in the coils.
More specifically, a hybrid synchronous motor with toroidal winding according to the present invention is characterized in that it comprises a rotor and a stator, the stator having at least one assembly (7) of coaxially displaced ferromagnetic rings (2, 3) which are cogged both on inner and outer circumferences thereof, and the assembly (7) being provided with a polyphase toroidal coil (6) made of coil segments so that a coil wire is lying between cogs (2a, 3a, 2b, 3b).
In the present invention, it is also characterized in that a plurality of the stator assemblies (7) have a common toroidal coil which is formed around all of them simultaneously, and wherein the common toroidal coil is wound around or assembled from U-shaped copper parts.
Further, in the present invention, it is characterized in that one pair of inner and outer rotor assemblies (16a, 16b) is mounted to each stator assembly (7), each stator assembly including two coaxially displaced rotor rings (17a, 18a or 17b, 18b), each rotor ring is being formed with rotor poles in the form of cogs which are equally spaced along a circumferential direction, so that the poles of each of the rotor rings (17a, 17b) are angularly shifted for one half of rotor pole division relative to the poles of the other corresponding one of the rotor rings (18a, 18b), respectively.
Furthermore, in the present invention, it is characterized in that either one axially magnetized disk is inserted between the cogged stator rings (2, 3) of each assembly (7), or two such disks are inserted between the adjacent cogged rotor rings (17a, 18a) and (17b, 18b), and wherein the disk or the disks are producing transverse magnetic flux in the inner and in the outer air gaps between the rotor and stator.
In addition, in the present invention, it is characterized in that four sets of rotor poles (19a, 19b, 20a, 20b) have the same number of poles, and four sets of stator poles (2a, 3b, 3a, 3b) also have the same number of poles, but these two numbers slightly differ if the stator poles are equally spaced along a circumferential direction.
While, in the present invention, it is characterized in that the gaps between rotor and stator are filled with a liquid, preferably ferromagnetic liquid which improves heat transport from motor interior and reduces mechanical vibrations.